A number of prior art systems are known for creating rectangular (X and Y) coordinates for information received in polar (azimuth and range) coordinate form. In one such converter the information is written onto a storage type cathode ray tube in polar format. Associated with the storage tube is an image orthocon tube which is typically scanned in raster scan format to provide essentially a rectangular coordinate format. Such converters are expensive, bulkly and not readily compatible with modern solid state systems.
U.S. Pat. No. 3,765,018 issued Oct. 9, 1973 to J. L. Heard et al., for example, describes an approach which may make use of the digital logic. In that patent a signal indicative of azimuth position is utilized to address read only memories which produce digital signals indicative of the sine and cosine of the particular azimuth. At each range position along the azimuth the value of the range is multiplied by the sine and cosine values to produce X and Y addresses in a digital memory at which the information at the particular azimuth and range is stored. Such a converter is capable of computing X and Y addresses relatively quickly but requires two relatively costly multiplier circuits.